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/* Timer_init()
*
* This routine initializes the timer on the IBM 386.
*
* Input parameters: NONE
*
* Output parameters: NONE
*
* NOTE: It is important that the timer start/stop overhead be
* determined when porting or modifying this code.
*
* COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994.
* On-Line Applications Research Corporation (OAR).
* All rights assigned to U.S. Government, 1994.
*
* This material may be reproduced by or for the U.S. Government pursuant
* to the copyright license under the clause at DFARS 252.227-7013. This
* notice must appear in all copies of this file and its derivatives.
*
* $Id$
*/
#include <rtems.h>
#include <bsp.h>
volatile rtems_unsigned32 Ttimer_val;
rtems_boolean Timer_driver_Find_average_overhead;
#if defined(pentium)
static inline unsigned long long rdtsc( void )
{
/* Return the value of the on-chip cycle counter. */
unsigned long long result;
__asm __volatile( ".byte 0x0F, 0x31" : "=A" (result) );
return result;
}
static void restore_timer( void )
{
CLOCK_ENABLE();
}
#else /* pentium */
rtems_isr timerisr();
#endif /* pentium */
void Timer_initialize()
{
static int First = 1;
#if defined(pentium)
if ( First ) {
extern int atexit( void (*)(void) );
First = 0;
/* Disable the programmable timer. */
CLOCK_DISABLE();
/* Try not to hose the system on return to DOS. */
atexit( restore_timer );
}
Ttimer_val = rdtsc();
#else /* pentium */
#define WAIT() \
{ \
Ttimer_val = 0; \
while ( Ttimer_val == 0 ) \
continue; \
Ttimer_val = 0; \
}
if ( First ) {
First = 0;
/* install ISR */
set_vector( timerisr, 0x8, 0 );
/* Wait for ISR to be called at least once */
WAIT();
/* load timer for 250 microsecond period */
outport_byte( TIMER_MODE, TIMER_SEL0|TIMER_16BIT|TIMER_RATEGEN );
outport_byte( TIMER_CNTR0, US_TO_TICK(250) >> 0 & 0xff);
outport_byte( TIMER_CNTR0, US_TO_TICK(250) >> 8 & 0xff);
}
/* Wait for ISR to be called at least once */
WAIT();
#endif /* PENTIUM */
}
#define AVG_OVERHEAD 0 /* 0.1 microseconds to start/stop timer. */
#define LEAST_VALID 1 /* Don't trust a value lower than this */
int Read_timer()
{
register rtems_unsigned32 total;
#if defined(pentium)
total = rdtsc() - Ttimer_val;
#else /* pentium */
register rtems_unsigned8 lsb, msb;
register rtems_unsigned32 clicks;
outport_byte( TIMER_MODE, TIMER_SEL0|TIMER_LATCH );
inport_byte( TIMER_CNTR0, lsb );
inport_byte( TIMER_CNTR0, msb );
clicks = msb << 8 | lsb;
total = Ttimer_val + (250 - TICK_TO_US( clicks ));
#endif /* pentium */
if ( Timer_driver_Find_average_overhead == 1 )
return total;
else if ( total < LEAST_VALID )
return 0; /* below timer resolution */
else
return total - AVG_OVERHEAD;
}
rtems_status_code Empty_function( void )
{
return RTEMS_SUCCESSFUL;
}
void Set_find_average_overhead(
rtems_boolean find_flag
)
{
Timer_driver_Find_average_overhead = find_flag;
}
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